Analysis of test questions: it is forbidden to dump domestic garbage and discharge industrial wastewater into rivers, which can prevent river water pollution, cause water pollution, destroy ecological balance and benefit ecological protection; Planting trees on both sides of the river can not only prevent wind and fix sand, but also improve the ecological environment and protect the ecological balance. Exotic species, such as water hyacinth, are stocked in rivers, which may cause the proliferation of exotic species and destroy the local ecological balance, because exotic species have no natural enemies in the local area.